The HIV and AIDS epidemic feeds on, and worsens, unacceptable situations of poverty, gender inequity, social insecurity, limited access to health care and education, war, debt and macroeconomic and social instability. The number of people living with HIV and AIDS continues to increase in several regions, most markedly in sub-Saharan Africa, the Pacific, Eastern Europe and Central Asia. The persistent nature of the epidemic and its increasing incidence in less powerful, more economically marginalised communities signals a need for a critical review of past policy and practice, particularly where this has left unchanged or worsened the risk environments that lead to new infection. Available evidence suggests that the caring and consumption burdens of AIDS have largely been met by households, limiting the capacities for future caring and mitigation of impact. Social cohesion or the collective networking, action, trust and solidarity of society, plays a positive role in reducing risk and dealing with vulnerability but is itself negatively affected by AIDS. This paper introduces the programme of work reported in this supplement of AIDS Care with an analysis of background evidence of community responses to HIV and AIDS. It explores how interventions from state institutions and non-governmental organizations (NGOs) support and interact with these household, family and community responses. How far is risk prevention reliant on individuals' limited resources and power to act, while risk environments are left unchanged? How far are the impacts of AIDS borne by households and extended families, with weak solidarity support? Where are the examples of wider social responses that challenge the conditions that influence risk and that support household recovery? Through review of literature, this background paper sets out the questions that the studies reported in this supplement have, in various settings, sought to explore more deeply.